1. Field of the Invention
This invention describes a novel gravity-independent exercise unit designed for use in microgravity, or on the ground, as a means by which to counter muscle atrophy and bone degradation due to disuse or underuse.
2. Description of the Relevant Art
Exposing humans to weightlessness during space flight induces significant structural and functional changes in the musculoskeletal system. These changes are manifested as muscle atrophy and bone degradation accompanied by neuromuscular changes including muscle fatigue and weakness, abnormal reflex behavior, and diminished neuromuscular efficiency, as noted by Nicogossian in xe2x80x9cCountermeasures to space deconditioning,xe2x80x9d Space Physiology and Medicine, Third Ed., eds. Nicogossian et al., Williams and Wilkins, Baltimore (1994), pp. 447-469. Support-unloading and structural changes of the muscle and bone seem to be the main causes of these functional abnormalities. See Booth and Criswell, xe2x80x9cMolecular events underlying skeletal muscle atrophy and the development of effective countermeasures,xe2x80x9d Int. J. Sports Med. 18[4], s265-s269 (1997); Convertino, xe2x80x9cExercise as a countermeasure for physiological adaptation to prolonged spaceflight,xe2x80x9d Med. Sci. Sports Exerc. 28[8], 999-1014 (1996); and Leblanc et al., xe2x80x9cMuscle atrophy during long duraction bed rest,xe2x80x9d Int. J. Sports Med. 18, s283-s285 (1997).
Reduced force development of skeletal muscle has been associated with six to eight percent decrements in volume of the lower limbs following flights longer than 3 months, according to Convertino, supra. Furthermore, because of the seven to twelve percent mineral loss in trabecular bone and throughout the spine after six to eight months of spaceflight, increased risk of bone fracture must be a concern for flight duration beyond 1 year. Id. As the future of long-term space habitation is inevitable, practical and effective measures to counter the debilitating effects of bone and muscle loss must be developed to allow astronauts to function normally in an environment without a 1-G gravity vector presence. This invention will further the objectives of the National Aeronautics and Space Administration (NASA) to develop successful exercise countermeasures for muscle atrophy and bone degradation during long-term microgravity habitation.
Recommendations to remedy the negative effects of microgravity on muscles and bones suggest that astronauts perform strengthening exercises while in space. See Booth, supra; Hoppeler et al., xe2x80x9cRecommendations for muscle research in space,xe2x80x9d, Int. J. Sports Med., 18: s280-s282 (1997); Hickson, et al., xe2x80x9cSkeletal muscle fiber type, resistance training, and strength-related performance,xe2x80x9d Med. Sci. Sports Exerc., 26[5]: 593-598 (1994); and Leblanc, supra. Such resistive exercises provide a load that is otherwise absent in space, presumably preserving musculoskeletal function. Many principles must be considered while designing an exercise device as a countermeasure for muscle atrophy due to disuse. Most importantly, load capabilities, constant force resistive output, and eccentric and concentric exercise capabilities should be the primary design goals of any resistive exercise device. (Eccentric exercise refers to the muscles"" lengthening during a contraction, while concentric exercise refers to the muscles"" shortening during a contraction. Both are essential during resistance training.) See Arnheim and Prentice, Principles of athletic training, Ninth Ed., McGraw-Hill, New York (1997); Baechle, T. R., Essentials of strength training and conditioning, National Strength and Conditioning Assn. (1994); Colliander and Tesch, xe2x80x9cEffects of eccentric and concentric muscle actions in resistance training,xe2x80x9d Acta Physiol. Scand. 140:31-39 (1990); and Harmen, xe2x80x9cResistance training modes: A biomechanical perspective,xe2x80x9d J. Strength and cond. Res. 4:59-65 (1994).
An extensive literature review has been performed on resistive exercise machines that have been designed for use in microgravity throughout the history of the space program. Numerous countermeasures for the negative physiological effects of microgravity on the muscluoskeletal system have been designed in the past, including exercise bikes, treadmills, and rubber band devices. See Convertine, supra; DiPramperno and Antonutto, xe2x80x9cCycling in space to simulate gravity,xe2x80x9d Int. J. Sports Med., 18(?): s324-326 (1997); Essfeld, xe2x80x9cThe strategic role of exercise devices in manned spaceflight,xe2x80x9d Micrograv. Sci. Tech, 3:180-183 (1990); Kreitenberg, et al., xe2x80x9cThe xe2x80x98Space Cyclexe2x80x99 self powered human centrifuge: A proposed countermeasure for prolonged human spaceflight,xe2x80x9d Aviat. Space Environ. Med. 69:66-72 (1998); and McArdle, supra. However, while these exercise devices provide essential aerobic activity, they lack the ability to provide the necessary resistive forces on muscles and bones to replace the gravity vector of Earth. The latest space countermeasures also use pneumatics or hydraulics for resistive exercise; however, these means of resistance often result in stammered movement patterns during exercise, as noted by Essfeld, supra. (Due to the nature of these devices, range of motion movements during exercise are not smooth.)
Furthermore, most hydraulic machines provide concentric muscle contractions, but lack the essential eccentric contractions during exercise. Id. Both muscle lengthening and shortening during contractions are desirable. Although rubber band devices do provide anaerobic concentric and eccentric resistive forces, they do not provide the measurable constant quantitative forces on the muscles that are necessary for optimal muscle maintenance. Additional exercise devices, such as the exercise ergometers, use dampers or friction to produce resistance concentrically, but require power to operate; however, power availability is limited on space flights. With a reported energy budget for the entire space station in the range of 70 kW and only 10 to 15 kW available for scientific experiments, the use of such powered motors is infeasible. See, e.g., Hoppeler, supra.
U.S. Pat. No. 4,208,049 discloses a xe2x80x9cmulti-functional exercising devicexe2x80x9d employing a number of constant load springs, which can be chosen individually or in combined groups to provide a selected constant load force on a foot or hand grip, movable bar or other mechanism. The force can be exerted in both directions of travel. The unit is large and bulky.
U.S. Pat. No. 5,226,867 discloses a user-manipulated modular exercise machine with two reel assemblies, each including a spirally-wound spring which applies to the reel a reactive torque of changing magnitude as the reel rotates in response to pulling input forces applied to a pull-cord by the user. A cam-operated spring compensating mechanism provides for essentially constant force during operations in various exercise modes.
U.S. Pat. No. 5,733,231 discloses an exercise apparatus including a number of inelastic, retractable cords, each having a handgrip. Retracting mechanisms are provided for retracting the cords, and separate resistance mechanisms are provided for each cord. Removable disk resistance units can be added to increase the resistance force, which can be made essentially constant. The units can be attached to a belt worn by the user, or in various other exercise devices.
U.S. Pat. No. 4,944,511 discloses a small xe2x80x9cadjustable resilient reel exerciserxe2x80x9d which includes right and left reels with their own foot pads, cords and hand grips. Outward pulling on the cords is resisted by spring packs containing clock-type coil springs, which can be adjusted to the same initial tension. The spring packs can be xe2x80x9cstackedxe2x80x9d on one another to vary the resistive force applied to the reels. The units can be used in exercise devices such as rowing machines. There is no suggestion of a constant force device.
U.S. Pat. No. 6,123,649 discloses a bulky treadmill having a resistance device attached to the frame and connectible to, e.g., the user""s legs, to provide a constant force resistance from the rear of the body while exercising.
U.S. Pat. No. 6,099,447 discloses an exercise belt for exercising the upper body, with cable retracting devices attached thereto. The cable retracting devices include coil springs whose tension is adjustable, but there is no mention of constant force devices. The ends of the cables include handles which may be weighted with detachable weights.
U.S. Pat. No. 5,540,642 discloses an aerobic exercise device including a platform which contains adjustable resistance devices from which cables can be withdrawn by the user in the course of exercising. There is no mention of constant force devices. The platform can be heavily weighted to increase stability.
U.S. Pat. No. 5,509,873 discloses an exercise device providing adjustable resistance through handles and retractable cords for the user""s hands. The device is worn on a belt. Two types of adjustable tension devices are disclosed, but there is no mention of constant force devices.
U.S. Pat. No. 3,596,907 discloses an exercise device including an elongated flexible member for mounting within a frame. Movement of the flexible member with respect to the frame is opposed by a force which gradually increases to a predetermined level, then remains at that level. The force is provided by a combination of friction and springs. The amount of predetermined force is adjustable. No significant force opposes the relative movement of the flexible member in the opposite direction.
U.S. Pat. No. 1,139,126 discloses an exercise machine using springs and friction to create an adjustable resistance against which the user exerts force by means of a cable or the like. The machine can be used as part of a rowing machine. There is no mention of a constant force device.
A xe2x80x9cconstant forcexe2x80x9d spring can be defined as xe2x80x9ca roll of pre-stressed strip which exerts a nearly constant restraining force to resist uncoiling.xe2x80x9d The force is stated to be constant because the change in radius of the curvature is constant. This is correct if the change in coil diameter due to buildup is disregarded. Constant and variable force springs are discussed in U.S. Pat. No. 6,149,094, which discloses a constant torque spring motor. FIGS. 8 and 9 of that patent illustrate the method for winding constant torque springs. The constant torque spring motor is a sophisticated, compact device which includes a take-up drum, and usually a larger diameter output drum, mounted on two separate axes. The spring itself is mounted upon the storage drum, which is free to rotate, while its opposite end is attached to the output drum. The spring coil is pulled straight, then wound onto the output drum by bending it against its natural curvature, thus storing energy in the reverse-coiled spring. When the output drum is released, the spring returns to its preset form, rewinding itself on the storage drum and rotating the output drum, thus imparting moment. The nearly constant torque provided results from the spring, which has been stressed sequentially during back-bending onto the output drum, releasing energy as it returns to the storage drum.
The Johnson Space Center Exercise Physiology Laboratory in Houston, Tex. has been evaluating the Interim Resistive Exercise Device (IRED) for use on the International Space Station (ISS) since about 1997. The resistive forces provided by the IRED are provided by xe2x80x9cflex packsxe2x80x9d which are composed of bungee and rubberband-type material. The IRED is capable of providing eccentric and concentric loading on the muscles during exercise; however, the loads are not constant throughout the entire range of motion of an exercise. Furthermore, to achieve a constant 1:1 eccentric:concentric ratio of exercise, the IRED will require the use of power. To date, there is no known gravity-independent resistive exercise unit that adheres to the requirements to provide a constant eccentric and concentric force during exercise. A need remains in the art for an apparatus that is capable of providing gravity-independent means of producing a measurable constant force, both eccentrically and concentrically, during exercise.
It is an object of the present invention to provide apparatus that is capable of providing a gravity-independent, measurable constant force both eccentrically and concentrically during exercise in terrestrial, microgravity and non-gravity environments.
It is also an object of this invention to provide apparatus that is capable of providing a gravity-independent, measurable constant force eccentrically and concentrically during exercise in any terrestrial or non-terrestrial environment, with or without the presence of gravity.
It is also an object of this invention to provide apparatus which can be used as a home gym for personal use, or as a supplement for rehabilitation programs.
The present invention will contribute to the development of practical and useful exercise countermeasures to muscle and bone atrophy during extended periods of inactivity or microgravity as a novel resistive exercise machine, the Constant Force Resistance Exercise Unit (CFREU). Unlike past and current countermeasure devices, the CFREU is designed to exercise muscle groups at a constant rate, both concentrically and eccentrically, throughout an entire range of motion during exercise.
In accordance with the present invention, a constant force resistive device is provided, comprising:
a hollow body containing:
at least one modular resistive pack, each of the pack(s) containing at least one constant torque spring, with
each spring wound upon a separate storage drum within the pack, and each spring within the pack(s) having the free end mechanically attachable to a single output drum within the pack(s);
each output drum having mechanical means for connection to an output shaft;
which output shaft is mechanically connected to a cable drum having a cable which can be withdrawn to rotate the drum,
with mechanical selection means provided for connecting any or all of the springs of the resistive pack(s) to the output shaft, thereby providing resistance to the withdrawal of a cable wound upon the cable drum.
The constant torque springs are flat coil springs wound according to their normal curvature upon the storage drums, and wound onto the single output drum(s) opposite their normal curvature. The hollow body can be configured to hold a plurality of modular resistive packs, with the output shaft and cable drum protruding outside the surface of the hollow body.
Each of the storage drums are preferably enclosed within the modular resistive pack(s). Each of the modular packs comprise an output shaft attached to the output drum and adapted for mechanical interconnection with the shafts of other adjacent packs so as to form a unitary output shaft, to which any of the packs can be engaged by operation of selection means.
Mechanical selection means for engaging the modular packs and their springs with the output shafts comprise plunger means which are removably connectible to the output drum of each of the packs to connect any of these drums to the output shaft and thus permit engagement of any or all of the modular packs with the output shaft. The plunger means can comprise spring-loaded plungers which are manually adjustable to engage the output shaft.
Further in accordance with the invention, each modular resistive pack can have an output drum which is mechanically attached to a common shaft, this shaft being mechanically connected to a cable drum having a cable which can be withdrawn to rotate the drum against the resistive force of the springs therein. The diameter of the cable drum and/or output drum(s) can be varied to vary the amount of resistive force offered by the modular packs which are engaged with the output shaft. Preferably, a plurality of modular packs and a cable drum of suitable diameter are provided so that resistive forces can be selected of at least about five pounds, preferably from about ten to about 300 pounds.
Still further in accordance with the invention, an alternate embodiment is provided wherein each constant torque spring in each of the modular resistive packs can be individually engaged or disengaged by lever-and-cam-actuated selection means which are adapted to removably connect and disconnect the output ends of any of the constant torque springs to the output drums of their respective packs. With this system, a plurality of modular packs and a cable drum mechanism can be adapted to provide resistive forces upon the cable of at least about five pounds, preferably in the range of from about five to about 500 pounds.
In both embodiments, the cable drums can be fitted with connection means such as rings or handles for a user to exert tension upon the cable in the course of exercising. Furthermore, each embodiment includes means for removably attaching at least one surface of the hollow body to at least one surface of a structure for use.
In either embodiment, the modular resistive packs can each comprise from one to about eight constant torque springs. In one preferred embodiment, the modular packs contain an output drum and one or two storage drums with the constant torque springs operationally connected therebetween, all components preferably being enclosed within the modular pack. In another embodiment, the packs comprise from about four to about eight storage drums spaced radially about the storage drum, again with constant torque springs operationally connected between the storage drums and the output drum.
In the embodiments with more than two storage drums and constant torque springs per modular pack, each output drum can be mechanically attached to a single output shaft, and each of the springs of each modular pack can be independently and separately engaged with the output drum of its respective pack to provide resistive force to the output shaft. In this embodiment, the springs can be selectively engaged or disengaged by lever-and-cam actuated selection means in which each incremental movement of the lever moves the cam means to expose a selection slot on the output drum and attach the output end of one of the springs to that selection slot. As with the embodiments above, the output shaft is mechanically connected to a cable drum having a cable which can be withdrawn in opposition to the resistive force of the engaged springs and packs. The cable can be directed by mechanical means comprising idler pulleys and roller means to suit the needs of the user.
Still further in accordance with the invention, a modular resistive pack is provided which comprises at least about four storage drums spaced radially about a central output drum, with each storage drum having a flat coil spring wound thereon according to its natural curvature, and means for selectively engaging or disengaging each spring to the output drum to be wound thereon opposite to the natural curvature of the springs as the output drum is rotated, plus means for connecting the output drum to an output shaft. The selection means are preferably lever-and-cam-actuated devices for removably attaching and detaching the output ends of the individual springs to the output drum.
The CFREU includes one trunk, generally a plurality of xe2x80x9cresistive packsxe2x80x9d, and a cable that is used during exercise. The unit essentially resembles a weight stack of a standard resistive exercise machine; however, because free weights are useless in microgravity, the constant resistive forces of the CFREU are provided by sets of constant torque springs that are arranged in modular resistive packs within the trunk.
The present invention allows for the following:
Ability to allow both eccentric and concentric muscle contraction during exercise;
Ability to provide a constant force over the entire range of motion of an exercise;
Ability to allow multiple exercises to be performed, thus maximizing a complete body muscle strengthening routine;
Safe to use, easy to operate during exercise, and uses no power to operate;
Accommodates various body heights and weights;
Resistive Packs are modular to allow for upgrades and exchanges; and
Can be used in microgravity and low-gravity environments.
The CFREU trunk can house any number of force packs that may be engaged or disengaged at any time to obtain the desired amount of resistive forces during exercise. A cable drum with a cable can be attached to the same shaft as the engaged force packs. The user can attach accessories such as leg cuffs, squat bars, harnesses, and handgrips to exercise various muscles. Additionally, the cable may be designed to split into two cable extensions so as to provide the user with bilateral exercise capabilities.
The resistive force provided by each resistive pack is based upon the activation of one or more constant torque springs. A constant torque spring is made up of a specially stressed constant force spring that travels between two drums. The spring is wound on a storage drum according to its natural curvature and is reverse wound to its natural curvature onto an output drum. The springs are rated in terms of torque (in-lbs.); therefore, the amount of force output depends on the moment arm of its output drum and the respective cable drum. In contrast to constant torque springs, constant force springs are simple coil springs which are wound upon a single storage spool and withdrawn directly from that spool. U.S. Pat. No. 4,208,049, columns xc2xe, explains the resulting resistive forces. Briefly, since the springs are rated in terms of torque, the force exerted on the user during exercise is given by F=M/r, where M=the sum of all torques from all springs in the engaged output drums, r=the radius of the cable drum or output drum, and F=force on user. The desired amount of resistive force encountered by the user should take into consideration the spring torque rating, inherent in the springs after manufacturing, and the diameter(s) of cable drums and output drums that will be used. Based upon the equation above, the total resistive force will vary according to the length of the moment arm (r=radius) of the cable drum and output drum(s). Since the spring resistive force felt by the user is directly related to its moment arm, changing the diameters of the cable and/or output drums will effectively change the force experienced by the user with a given set of springs engaged. Since the relation is inverse, decreasing the drum diameters will increase the resistive force, while increasing these diameters will decrease the resistive force.
The resistive packs are designed to be modular, so if a spring were to fatigue and break inside its resistive pack, the pack could be unlocked from its base and safely exchanged for a new pack. Although the springs themselves may be exchanged or replaced within the packs, it is preferred to replace the modular packs for convenience. Easy exchangeability of the resistive packs also allows for pack upgrades to higher or lower resistive forces specific to individual exercise preferences. Resistive packs can be held together in series by coupling each resistive pack output shaft to the next. Examples of constant torque springs are disclosed in U.S. Pat. No. 4,208,049, which is incorporated herein by reference.
The resistive force provided by each resistive pack varies per pack specification. The CFREU resistive packs are designed so that the user can select one or more at one time to achieve the desired amount of resistive forces during a given exercise. Additionally, the total resistive force output of each resistive pack can vary according to individual specifications. With the addition of more springs or resistive packs, the CFREU can provide an essentially unlimited amount of resistive force which can be utilized for eccentric/concentric exercise.
In addition to uses within the space program, the compact resistive packs of the CFREU allow the unit to be small enough for easy use as a home gym for personal use, or as a supplement for rehabilitation programs. Such resistive packs may be obtained individually by a consumer, and may be changed conveniently out of the CFREU according to the desired exercise regimen. Thus, the resistive packs replace the need for expensive, heavy, and bulky traditional weight plates. The CFREU may be employed by hospitals, rehabilitation and physical therapy clinics, and other related professional businesses.
The CFREU includes a series of resistive packs that can be coupled to each other by the interconnection of each pack""s output shaft. Thus, when all the resistive packs are coupled together, one complete output shaft is formed that runs the length of the CFREU. At the end(s) of the output shaft, at least one cable drum is attached that provides at least one cable to the user for use during exercise. Cable drums and/or pack output drums of different sizes can be provided to affect the amount of resistive force exerted by a given set of constant torque springs. Each resistive pack has a selection plunger device that is used to engage or disengage that pack. To engage a resistive pack for use during exercise, the user inserts the selection plunger through the selection mechanism and engages the output shaft of the individual pack. As the selection mechanism is directly attached to the output drum, this causes the output drum to engage to the output shaft, thus putting the output drum into motion. Since the constant torque springs are attached to the output drum, the rotation of the output drum activates the constant torque springs to reverse rewind around the output drum, thus translating the spring forces along the output shaft to the cable drum. Because the cable drum is attached to the output shaft, the user receives the selected resistive packs"" combined resistive forces during exercise when pulling on the cable. When a resistive pack is not in use (disengaged), the plunger device rests embedded in the selection mechanism, but is not inserted into the output shaft. Since the selection mechanism is not engaged, the output shaft simply rotates while the output drum remains stationary.
Each constant torque spring is housed or wound on its own storage drum, which rotates on its own storage drum shaft within each resistive pack. If a spring were to fatigue and break inside its pack, the pack could be unlocked from its base within the trunk and safely exchanged for a new pack. Easy exchangeability of the resistive packs also allows for convenient resistive pack exchanges to provide higher or lower resistive forces specific to individual exercise preferences.
Each resistive pack has a mechanical selection mechanism, preferably employing spring-loaded retractable plungers, that allows the user to select which resistive pack(s) he/she would like to use during exercise. The selection mechanism allows for any one or more resistive packs to be selected at one time, thus providing many combinations of resistive force available from the CFREU. The force is exerted as a resistance to withdrawal of the cable by the user, and remains essentially constant during the full range of motion for a given combination of resistive force packs.
The user can attach conventional exercise accessories such as leg cuffs, squat bar, harness, and handgrips to the cable(s) for exercising various muscle groups. The CFREU can also be incorporated into full body cable and pulley exercise systems.